[LeetCode-13]-Roman to Integer (将罗马数字转换为整数)【附源码】_donaldsy

 

 

题目相关

【题目解读】
将罗马数字转换为整数,其中「I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000」。IV、IX、XL、XC、CD、CM这几种情况需要做减法,要特殊处理。

【原题描述】原题链接
Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

 Symbol       Value  I             1  V             5  X             10  L             50  C             100  D             500  M             1000 

For example, two is written as II in Roman numeral, just two one’s added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.

Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:

I can be placed before V (5) and X (10) to make 4 and 9.
X can be placed before L (50) and C (100) to make 40 and 90.
C can be placed before D (500) and M (1000) to make 400 and 900.
Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.

Example 1: Input: "III" Output: 3  Example 2: Input: "IV" Output: 4  Example 3: Input: "IX" Output: 9  Example 4: Input: "LVIII" Output: 58 Explanation: L = 50, V= 5, III = 3.  Example 5: Input: "MCMXCIV" Output: 1994 Explanation: M = 1000, CM = 900, XC = 90 and IV = 4. 

【难度】Easy

Solution

该题比较直观,采用的是逐个遍历并通过switch判断,遇到IV、IX、XL、XC、CD、CM这些情况时再恢复数据。

采用switch代码逻辑清晰,不好的是代码过长。

该程序耗时: 16 ms,运行时间超过了99.46 % 的C++提交代码,内存使用情况超过100%的C++代码。

下面是程序代码:

    int romanToInt(string s)     {         int ret = 0;         for (size_t i = 0; i < s.size(); i++)         {             /* code */             switch (s[i])             {                 //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'I':                 ret += 1;                 break;                  //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'V':                 ret += 5;                  if (s[i - 1] == 'I')                 {                     //IV的这种情况需要恢复                     ret -= 2;                 }                 break;                 //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'X':                 ret += 10;                 if (s[i - 1] == 'I')                 {                     //IX的这种情况需要恢复                     ret -= 2;                 }                 break;                  //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'L':                 ret += 50;                 if (s[i - 1] == 'X')                 {                     //XL的这种情况需要恢复                     ret -= 20;                 }                 break;                  //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'C':                 ret += 100;                 if (s[i - 1] == 'X')                 {                     //XC的这种情况需要恢复                     ret -= 20;                 }                 break;                  //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'D':                 ret += 500;                 if (s[i - 1] == 'C')                 {                     //CD的这种情况需要恢复                     ret -= 200;                 }                 break;                  //I = 1; V = 5; X = 10; L = 50; C = 100; D = 500; M = 1000             case 'M':                 ret += 1000;                 if (s[i - 1] == 'C')                 {                     //CM的这种情况需要恢复                     ret -= 200;                 }                 break;              default:                 return 0;             }//end switch         }//end for          return ret;     } 

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[LeetCode-13]-Roman to Integer (将罗马数字转换为整数)【附源码】_donaldsyLeetCode发现一个新技能,点按上面直方图中的内容,你将会看到这个分部下的其他人的代码情况。如下图所示,点击后将从LeetCode服务器上获取代码该运行时间下的代码,方便学习大牛的代码
[LeetCode-13]-Roman to Integer (将罗马数字转换为整数)【附源码】_donaldsy

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[LeetCode-13]-Roman to Integer (将罗马数字转换为整数)【附源码】_donaldsy

 

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